If a clot forms in a diseased coronary artery, oxygen no longer flows to the part of the heart muscle that is supplied by the artery. The lack of oxygen causes angina and leads to a heart attack. Aspirin plays an important role in the treatment of angina and heart attack. It reduces the risk for the formation of a clot in the narrowed coronary artery by interrupting the clotting process.

Those who have angina can reduce the risk of a heart attack by 50% by taking aspirin. Aspirin also reduces the risk of death by 25% in those who have severe coronary artery disease.